Experimental insight into the chemical corrosion mechanism of copper with an oil-in-water emulsion solution

Chemical corrosion mechanism of copper in an oil-in-water (O/W) emulsion is worthy of study since it would contribute to emulsion-lubrication in a metal-working process and for copper storage. The immersion experiments were carried out and the corrosion rates were measured using the weight-loss method. Surface morphology of the copper specimen was observed using a scanning electron microscope (SEM). The compositions of the corrosive residues were analyzed using an energy dispersive spectrometer (EDS) and an X-ray photoelectron spectrometer (XPS). It was found that the corrosion rate of copper in an emulsion linearly increases and the kinetics relationship could be deduced as D₁ = 2.66 × 10⁻³t^11.68 at room temperature (25 °C). After 1488 h of immersion time, the corrosion products on the copper surface were determined to be Cu₂O, CuO, Cu(OH)₂, CuCO₃ and Cu₂(OH)₂CuCO₃, which also changed the appearance of the emulsion. During adsorption, copper is more likely to coordinate with hydroxide, carboxylate or ester anions to generate copper compounds. The surfactants were consumed and the efficiency of emulsification characteristics was lost and finally, the O/W emulsion separated into two layers, which might hint the significance of introducing an inhibitor to protect the copper surfaces.

Chemical corrosion mechanism of copper in an oil-in-water (O/W) emulsion is worthy of study since it would contribute to emulsion-lubrication in a metal-working process and for copper storage.     

Fabrication of photo-Fenton self-cleaning PVDF composite membrane for highly efficient oil-in-water emulsion separation

The anti-fouling performance of membranes is an important performance in the separation of oil/water. However, the membrane with anti-fouling performance will also have surface scaling phenomenon when it runs for a long time. Therefore, there is still a great demand for stain-resistant membranes with good self-cleaning ability and high flux recovery rate. Based on this, this paper firstly prepared a hydrophilic membrane with carboxyl group and carboxyl ion by blending poly(ethylene-alt-maleic anhydride) (PEMA) and polyvinylidene fluoride (PVDF), and then prepared a self-cleaning composite membrane by in situ mineralization of β-FeOOH particles on the surface of the membrane for efficient oil-in-water emulsion separation. A large number of –COOH/COO⁻ and β-FeOOH particles on the membrane surface make the composite membrane have strong hydrophilic properties (WCA = 20.34°) and underwater superoleophobicity (UOCA = 155.10°). These composite membranes have high separation efficiency (98.8%) and high flux (694.56 L m⁻² h⁻¹ bar⁻¹) for soybean oil-in-water emulsion. Importantly, the as-prepared membrane shows excellent flux recovery rate (over 99.93%) attributed to the robust photo-Fenton catalytic activity of β-FeOOH, and the β-FeOOH is chemically bonded to the as-prepared membrane, which makes the as-prepared membrane have good reusability. This work provides hope for the application of self-cleaning membranes in the construction of anti-fouling membranes for wastewater remediation.

The anti-fouling performance of membranes is an important performance in the separation of oil/water.     

Effect of electric field on coalescence of an oil-in-water emulsion stabilized by surfactant: a molecular dynamics study

The microscopic understanding of electrocoalescence of oil-in-water (O/W) emulsions stabilized by surfactant is very important to improve the efficiency of electrical demulsification. The behaviors of the coalescence of O/W emulsion stabilized by surfactant in the presence of a direct electric field and a pulsed electric field were explored by nonequilibrium molecular dynamics simulations. According to the simulated results, an electrical method is feasible to demulsify an O/W emulsion stabilized by a surfactant. The configuration and movement of the sodium dodecyl sulfate (SDS) were determined by interactions between SDS molecules themselves and between SDS and oil/water molecules along with the force exerted by the applied electrical field. Two droplets will coalesce into one when the strength of the electric field exceeds 0.4 V nm⁻¹. The SDS group can be broken up by an electric field larger than 0.6 V nm⁻¹. The point when interaction energy between the hexadecane molecules of the two droplets begins to decrease from zero is consistent with the time when the two oil droplets came in contact. The coalescence process can be completed if the two droplets have begun to coalesce, even after the electric field was removed. Otherwise, the coalescence process cannot be completed. To enhance the efficiency of the electrocoalescence of O/W emulsions, strength, frequency and duty ratio of the electric field have to be optimized according to the properties of the emulsion. This research will help us to figure out how electric fields promote the efficiency of electrocoalescence of O/W emulsions with surfactant.

The microscopic mechanisms of electrocoalescence of O/W emulsions stabilized by surfactant were analyzed from the electric dipole moment of the surfactant, the interaction between surfactant and oil molecules and the deformation of the surfactant.     

Impact of nanoparticle surface modification on the mechanical properties of polystyrene-based nanocomposites

Nanocomposites consisting of metal oxide nanoparticles in a polymeric matrix enable the improvement of material properties and have become highly relevant for numerous applications, such as in lightweight structures with an enhanced Young''s modulus for automotive and aircraft applications. The mechanical properties can be adjusted by controlling the amount of particles, their degree of agglomeration and their direct interaction with the matrix. Whilst the latter aspect is particularly promising to achieve high reinforcement at low filler contents, the mechanisms behind this effect are still not fully understood, preventing the rational design of a particle–polymer system with customized properties. In this work, a two-step modification strategy is used to tailor the particle–matrix interface via chemical groups bound to the surface of zirconia nanoparticles. Two modifications featuring terminal vinyl functions as potentially polymerizable groups are compared. Moreover, an inert reference modification is used to determine the influence of the terminal vinylic groups. In contrast to previous studies, all groups are covalently linked to the particle surface, thereby excluding effects such as detachment or weak coordination and ensuring that changes in the mechanical properties can be correlated to chemical groups on the particle surface. After embedding modified particles in polystyrene, the mechanical properties as well as the cross-linkage between the particles and the matrix are characterized, clearly showing the significant impact of a covalent particle–matrix linkage, with an increase of the Young''s modulus by up to 28% with only 3 wt% filler content.

A two-step modification strategy is applied to tailor the particle–matrix interface in zirconia nanoparticle–polystyrene composites, achieving strongly enhanced mechanical properties.     

Modulating the magnetic properties of MoS2 monolayers by group VIII doping and vacancy engineering

In this work, density functional theory is adopted to study the electronic and magnetic properties of MoS₂ monolayers combined with a single S vacancy defect and a group VIII (G8) atom dopant, in which the dopant is incorporated via Mo substitution. The calculated results show that the magnetic properties of monolayer MoS₂ can be tuned by changing the distribution of the G8 atom and S vacancy. The S vacancy tends to decrease the net magnetic moment of the doped system when these two defects are in their closest configuration. By adjusting the distance between the dopant and the S vacancy, the doped MoS₂ monolayer may show a variable net magnetic moment. In particular, all of the Ni-doped MoS₂ monolayers show zero magnetic moment with or without an S vacancy. The mean-field approximation is used to estimate the Curie temperature (T_C). Our results show that Fe, Co, Ru, Rh, Os and Ir-doped MoS₂ monolayers are potential candidates for ferromagnetism above room temperature. The density of states calculations provide further explanations as to the magnetic behavior of these doped systems. These results provide a new route for the potential application of atomically thin dilute magnetic semiconductors in spintronic devices by employing monolayer MoS₂.

In this work, the density functional theory study shows that the magnetic properties of MoS₂ monolayer can be tuned by the distribution of group VIII atom and S vacancy, in which the dopant is incorporated via Mo subsitution.     

Superhydrophilic fluorinated polyarylate membranes via in situ photocopolymerization and microphase separation for efficient separation of oil-in-water emulsion

A superhydrophilic modified fluorinated polyarylate membrane with high tensile strength was prepared by a combination of in situ photocopolymerization and microphase separation. The as-prepared membrane was successfully utilized for oil-in-water emulsion separation with high separation efficiency and high flux. Furthermore, the membrane displayed excellent antifouling performance and recyclability for long-term use.

We have developed a novel superhydrophilic FPAR membrane with high tensile strength by in situ photocopolymerization and microphase separation, which can effectively separate oil-in-water emulsions with high separation efficiency and flux.

Today, the ever-growing serious environmental pollution caused by oil-contaminated water from the daily life of people as well as from industries demands the search for novel materials and strategies to realize oil/water separation with high efficiency.^1–5 Traditional separation technologies such as gravity separation, centrifugation, skimming, sedimentation, and flotation are useful for most of the separation processes. Unfortunately, low separation efficiency, high energy consumption and complex equipment have restricted the application of these technologies to some extent.^6–8 Other than that, it may be very difficult for them to separate emulsified oil/water solutions.⁹ Therefore, desirable materials for effective separation of oil/water emulsions are urgently needed. As a result, filtration polymer membranes have been considered to be a suitable technology for separating various emulsions, but suffer from low flux, surface fouling and poor mechanical properties.^2,9Recently, significant interests have been attracted to the design and preparation of oil/water separation membranes with special wettability by a combination of rough structure and surface chemistry.^2,10–14 Typically, these polymer membranes may be classed into two types, polymer coated mesh membranes and polymer porous membranes.^3,15–22 For polymer coated mesh membrane, it requires a mesh as a support which is capable of improving mechanical properties and rendering a micro-scale porous structure.² For example, Tuteja and co-workers developed a superhydrophobic mesh membrane coated with a blend of cross-linked poly(ethylene glycol)diacrylate and fluorodecyl polyhedral oligomeric silsesquioxane, which was valuable for separation of oil/water emulsions with droplet sizes larger than 1 μm.²¹ PVDF has been acknowledged as one of the main materials for manufacturing polymer porous membranes for separation of oil/water emulsions through a phase-inversion process.^1,2 In 2014, a superhydrophilic and underwater superoleophobic poly-(acrylic acid)-grafted PVDF (PAA-g-PVDF) membrane was fabricated by a salt-induced phase-inversion approach and applied to oil-in-water emulsions, however, the tensile strength of this membrane was not more than 0.64 MPa, which limited their practical applications.²²Polyarylate, a family of high-performance polymers, noted for their strength, toughness, chemical resistance, and high melting points.^23–26 Recently, Livingston and co-workers have demonstrated the formation of crosslinked polyarylate microporous membranes which have great potential for applications in molecular separations.²⁷ In previous studies, our group developed a simple procedure to fabricate a superhydrophobic and superoleophilic porous polyarylate membrane which could effectively separate oil/water mixtures.²⁸ In this communication, we reported the fabrication of a novel superhydrophilic sodium acrylate modified fluorinated polyarylate (SFPAR) membrane for efficient separation of oil-in-water emulsion by a combination of in situ photocopolymerization and microphase separation. It was very exciting that the as-prepared SFPAR membrane exhibited prominent mechanical strength and outstanding water permeability. Furthermore, the membrane also displayed excellent underwater superoleophobicity, antifouling performance and recyclability for long-term use, which highlight its potential for practical applications. Fig. 1 shows the formation of a SFPAR membrane via in situ photocopolymerization for endowing with the hydrophilic property of FPAR (Scheme 1a–c), followed a microphase separation (Scheme 1d and e) for obtaining the SFPAR membrane with porous structure. The experiments are described in detail in the ESI.^† Here, in situ photocopolymerization was applied for getting hydrophilic FPAR, which have the following advantages: good dispersibility of the formed acrylate copolymer in the FPAR matrix, low reaction temperature, and shortening the preparation time of membrane. After a microphase separation and a drying process, a white membrane was obtained by peeling from a substrate (Scheme 1f).Open in a separate windowFig. 1Water contact angle of the FPAR membranes as function of sodium acrylate mass fraction (a), water contact angle of the SFPAR and FPAR membranes as function of time (the insets are photographs of water drops on the membrane surfaces) (b), underwater–oil contact angle (c and d) and dynamic underwater–oil-adhesion of the SFPAR membrane (e and f). The underwater–oil contact angle were measured with 4 μL hexadecane droplet.Open in a separate windowScheme 1Schematic of the formation of a SFPAR membrane via in situ photocopolymerization and a limited micro-phase separation. The fluorinated polyarylate (FPAR) was fabricated by interfacial polymerization of bisphenol AF, terephthaloyl chloride, and isophthaloyl chloride (Fig. S1a^†). The number-average molecular weight of the obtained PAR is 93 000 and the polydispersity index is 1.76 (Fig. S2^†). The experiments are described in detail in the ESI.^†One of the main purposes of in situ photocopolymerization is to improve the wettability of FPAR by introducing carboxylate salts (Fig. S1b^†). Fig. 1a shows water contact angle of the FPAR membranes as function of sodium acrylate mass fraction. The results indicated that the value of water contact angle on the FPAR surface significant decreased with the increase of the sodium acrylate content. After the sodium acrylate content exceeded ∼9.5 wt%, the contact angle tended to equilibrium, less than ∼1°, which formed a superhydrophilic modified FPAR membrane (SFPAR). To further examine the wettability of water on the FPAR membranes, the water contact angles of the FPAR and SFPAR membrane as function of time was also measured (Fig. 1b). The pure FPAR membrane had the initial water contact angel of approximately 96.2° and the value of water contact angel almost kept stable after 100 s, exhibiting good hydrophobicity. On the contrary, the approach to introducing carboxylate to FPAR caused a significant differences. The SFPAR membrane had the initial water contact angel of approximately 40°. Interestingly, the value of water contact angel of the SFPAR membrane rapidly decreased to ∼1° in less than 7 s, illustrating outstanding superhydrophilicity, which is caused by the introduction of carboxylate sodium and the porous structure of the SFPAR membrane. Furthermore, the underwater–oil contact angle (OCA) and dynamic underwater–oil-adhesion of the SPAR membrane were also studied (Fig. 1c and d). An oil droplet was lifted up and contacted the SPAR membrane surface under water (Fig. 1c and d). It was observed that the oil droplet remained spherical and the underwater–OCA of this membrane is ∼161.7°, demonstrating excellent underwater superoleophobicity. From Fig. 1e to Fig. 1f, the oil droplet was forced to adequately contact the membrance surface and then moved to the left. During the moving process, the spherical oil droplet had no obvious deformation, also showing that the SPAR membrane had excellent antiadhesion to oil.ATR-FTIR spectra of the SFPAR and FPAR membranes are shown in Fig. 2a. For ATR-FTIR spectrum of the SFPAR membrane, besides the corresponding absorption peak of FPAR, The characteristic stretching peaks were obviously shown at 2850–3000 cm⁻¹ and 1457 cm⁻¹, respectively, resulting from –CH₂– and –CH₃, and –O–CH₂– groups of the crosslinked acrylate copolymer prepared by in situ photocopolymerization. The peak at 1569 cm⁻¹ was the asymmetric CO²⁻ (salts) stretching vibration in –CO₂Na of the formed acrylate copolymer. Moreover, the peak at 1640 cm⁻¹, which was attributed to the stretching vibration of vinyl bond, was not observed from the ATR-FTIR spectrum of the SFPAR membrane, indicating that the monomers were polymerized.Open in a separate windowFig. 2ATR-FTTR spectra of the SFPAR and FPAR membranes (a) and the overall XPS spectra of the SFPAR and FPAR membranes (b).XPS was performed to examine the surface chemical composition. Fig. 2b exhibits the overall XPS spectra of the SFPAR and FPAR membranes. There were three signals on the surface of the FPAR membrane attributed to C, O and F element whose atomic percentage was approximately 66.0, 20.6, and 13.4%, respectively. In comparison with the XPS spectrum of FPAR, the new signal appearing in the spectrum of the SFPAR membrane was attributed to Na element. The percentage of Na was estimated to be approximately 4.5 wt%, higher than the bulk content (2.3 wt%), and the F content of SFPAR membrane was obvious decreased and the O content is increased after in situ photocopolymerization, indicating the obvious surface enrichment of sodium carboxylate groups in the SFPAR membrane. Fig. 3 displays SEM images of the surface and cross section of the FPAR and SFPAR membranes. Apparently, the morphologies of the SFPAR membrane are different from those of the FPAR which can be attributed to the thermodynamics instability and the non-solvent Induce phase separation. The FPAR surface is smooth (Fig. 3a), while the SFPAP surface is porous and has a great number of micro nano-scale pores (Fig. 3c) and the pore size and pore distribution were calculated by Nano Measurer 1.2 (Fig. S3a^†). For the cross of the FPAR and SFPAR membranes, the former is dense and few pores can be found (Fig. 3b). However, the latter is loose and possesses many inter-connected nano-scale channels with a diameter of 50–200 nm (Fig. 3d). Different from the reported superhydrophilic membranes made from semicrystalline PVDF,^22,29,30 the FPAR is amorphous. According to the XPS and SEM results above, the possible formation mechanism of SFPAR membranes with porous structure prepared by in situ photocopolymerization and phase separation can be described as follows. As can be seen from Scheme 1, the FPAR, the monomers (BA, SA and TEGDA) and photoinitiator are first dissolved in THF to form the homogenous viscous solution (Scheme 1a and b). After in situ photocopolymerization of BA, SA and TEGDA occurs at room temperature, the crosslinked polyacrylate containing sodium carboxylate groups come into being in the viscous solution (Scheme 1c). During the immersion process (Scheme 1d), with the extraction of THF by the coagulation bath, the blend matrix of the amorphous FPAR and the crosslinked polyacrylate will gradually shrink and solidify. Simultaneously, a microphase separation occurs in the blend matrix due to the crosslinking of polyacrylate and the thermodynamics instability. Furthermore, sodium carboxylate groups attached to the polyacrylate network can absorb enough water in the blend matrix, ultimately leading to the formation of the wet membrane containing water. During the drying process, water is evaporated from the wet membrane and the porous structure appears in the membrane because the solidification of FPAR matrix restricts the movement of the polyacrylate segments. Finally, the SFPAR membrane with porous structure is obtained after the blend matrix is fully dried at room temperature (Scheme 1e and f). The hydrophilic sodium carboxylate groups will enrich in the SFPAR membrane surface and the inner surface of the micro nano channel due to the driving forces of surface free energy and hydrophilicity/hydrophobicity interactions (Fig. S3b, ESI^†), which makes it possible for the preparation of oil–water separation membrane.Open in a separate windowFig. 3SEM images of the FPAR and SFPAR membranes: the surface (a) and cross section (b) of the FPAR membrane; the surface (c) and cross section (d) of the SFPAR membrane. The inset is high-magnification SEM image of the SFPAR membrane surface.In this work, oil–water separation of the SFPAR membrane was carried out with a vacuum driven filtration system at 0.07 MPa. Toluene-in-water emulsion was employed to evaluate the separation ability of the membrane and the droplet size distribution of the emulsion is in the range from ∼900 nm to ∼8 μm (Fig. S4, ESI^†). Fig. 4a illustrates a self-made separation device and the separation result of toluene-in-water emulsion (the separation experiments are described in detail in the ESI^†). Compared with the milky white feed emulsion (up), the filtrate (down) is colorless from the appearance. A noticable difference was observed between the feed and the filtrate by the optical microscopy images. There appear a great many droplets in the image of the feed before filtration, however, no droplet can be viewed for the filtrate. Furthermore, the characteristic peak of toluene for the filtrate is not observed from UV-VIS spectrometer (TU-1901, Beijing Purkinje General Instrument Co., Ltd, China) in comparison with the feed (Fig. S5, ESI^†), and the oil content in the filtrate is 54 ± 17 ppm measured by a total organic carbon analyzer, indicating that the as-prepared membrane can successfully separate oil/water emulsion with high efficiency. The other two emulsions also have good separation efficiency (Table S1, ESI^†).Open in a separate windowFig. 4The vacuum driven filtration system and separation results for toluene-in-water emulsion (a) and change of the flux and flux recovery in the separation of a toluene-in-water emulsion over five cycles (b).Taking advantage of the reported method,^22,29 the flux and the antifouling property of the membrane were measured by the vacuum driven filtration system. Continuous separation of the toluene-in-water emulsion lasts for approximately 30 hours over five cycles and the flux is detected every an hour and six points were taken down within each cycle. The SFPAR membrane is gently washed by using DI water to dispose of surface adsorbent. As shown in Fig. 4b, the flux has a slight decline from ∼3800 to ∼3600 L m⁻² h⁻¹ within one cycle. Nevertheless, the membrane can recover fully to the initial flux after it is washed by water. The results show that the SFPAR membrane possesses a high flux and an outstanding antifouling performance for long-term use. Further studies will focus on the regulation of the pore size of the SFPAR membrane and get the most proper selectivity and penetration. Moreover, as one of the important factors in practical application, the tensile strength of the membrane was also tested by a testing machine (Fig. S6, ESI^†). Due to the porous structure, the tensile strength of the SFPAR membrane is ∼6.02 MPa, less than that of the FPAR membrane (∼27.59 MPa). However, the SFPAR membrane still has high mechanical property compared with the reported hydrophilic modified PVDF oil/water separation membrane.^14,17In conclusion, we have developed a novel superhydrophilic modified FPAR membrane with porous structure by in situ photocopolymerization of acrylate monomers and subsequent microphase separation. The results of ATR-FTIR and XPS demonstrated that sodium carboxylate groups was immobilized in the FPAR membrane by in situ photocopolymerization. When the sodium acrylate content was beyond ∼9.5 wt%, the as-prepared SFPAR membrane exhibited prominent superhydrophilicity, underwater superoleophobicity, and water permeability. The SFPAR membrane could effectively separate oil-in-water emulsions with high separation efficiency and high flux. Significantly, the obtained membrane possessed a good antifouling property and could be recycled for long-time use. From a practical perspective, the SFPAR membrane had a higher mechanical strength than traditional hydrophilic polymeric membranes with similar permeation properties. Therefore, we anticipate that our membrane will have high potential in practical application for treating wastewater from the daily life and industries.     

Identifying the mechanical properties of tissue by ultrasound strain imaging

A new elastography method is presented that images the mechanical properties of soft tissue. The tissue is externally vibrated over a range of frequencies simultaneously and the resulting displacement is recorded at multiple locations and time instants with a sequence of ultrasound images. Two methods are proposed for estimating the mechanical properties from the recorded data. In the first method, equations of motion are written for a tissue model of masses, springs and dampers. The equations are solved to identify the model parameters and construct an image. The second method performs a transfer function analysis of the tissue motion. The tissue properties are identified from the shape the of transfer function. Simulations show good performance of the new method compared with static elastography. Initial experimental results from homogeneous and layered tissue phantoms also demonstrate the ability quantitatively to image tissue stiffness. Preliminary results are obtained for viscosity and density estimation. Further work is needed to extend the formulation to 3-D and improve robustness of the viscosity and density estimates.     

Microstructure design of polypropylene/expandable graphite flame retardant composites toughened by the polyolefin elastomer for enhancing its mechanical properties

The enhanced toughness of flame-retardant polymer composites is still a big challenge due to the deterioration of their mechanical properties. In this work, polypropylene (PP)/nanohybrid expandable graphite (nEG) flame-retardant composites toughened by octene–ethylene copolymer (POE) were fabricated for obtaining good mechanical properties and flame retardancy. The structure, rheological and crystallization behaviors, morphology, flame retardancy, and mechanical property of PP/nEG/POE composites with different contents of POE were investigated. Results show that the elongation at break and impact strength of PP composites were significantly improved due to the incorporation of POE. The elongation at break and notched impact strength of toughened PP composites with only 20% POE were increased to 521.6% and 22.9 kJ m⁻² from 16.1% and 9.3 kJ m⁻² for untoughened PP composites, respectively. The scanning electron micrography (SEM) images showed that POE droplets were dispersed finely and uniformly in the PP matrix, exhibiting a typical two-phase structure. Additionally, the interfacial adhesion between the matrix and inorganic particles was enhanced due to the addition of POE. The rheological behaviors of PP composites showed improved elasticity and longer relaxation times, and a stress-yield behavior appeared with the addition of POE. The interfacial interaction in PP composites was enhanced and the formation of an interparticle network was further proved. Additionally, the toughened PP/nEG20 composites with different contents of POE exhibited excellent flame retardancy. Therefore, the toughened flame-retardant PP composites should possess a wider range of application potential.

The enhanced toughness of flame-retardant polymer composites is still a big challenge due to the deterioration of their mechanical properties.     

Preparation and properties of a stable intravenous lorazepam emulsion

Lorazepam is normally administered as a solution in organic solvents such as propylene glycol. This type of formulation is undesirable. This study describes the development of a parenteral emulsion formulation for lorazepam. The stability of lorazepam in the emulsion was examined. Ten per cent corn oil emulsions stabilized with egg lecithin, Pluronic F68 and Pluronic F88 were used. The incorporation of lorazepam does not appear to destabilize the emulsion, and lorazepam itself appears to be stable for at least 1 year in this liquid formulation.
Haemolysis caused by emulsion formulations containing lorazepam and different emulsifiers was evaluated using human and rabbit blood to assess their safety as parenteral drug carriers. The results show that the emulsions did not have any significant haemolytic activity whereas organic solvents and solutions of lorazepam in organic solvents caused substantial haemolysis.     

假肢接受腔内衬套的细胞毒性及力学性能检测

目的 调查研究国内市售假肢接受腔内衬套的细胞毒性及力学性能现状。方法 收集国产厚度6 mm泡沫内衬(A)、国产厚度5 mm EVA泡沫内衬(B)、德国产厚度5 mm EVA泡沫内衬(C)、德国产厚度12 mm PE泡沫内衬套(D)、冰岛产厚度3 mm硅胶内衬套(E)、德国产厚度4 mm凝胶内衬套(F)。应用显微镜观察与噻唑蓝比色法,进行不同内衬套细胞毒性检测。采用高锰酸钾消耗测定有机小分子物质含量。采用材料力学试验机对内衬套材料进行拉伸强度、扯断伸长率(%)、100%定伸强度的检测。采用邵氏硬度计进行硬度测试。结果 内衬套A、B、C和D的细胞毒性反应均为2级,内衬套E和F的细胞毒性反应均为0级。内衬套A、B、C高锰酸钾消耗量均超过150 mg/kg。除内衬套C外,其余5种产品硬度均≤70 HA。除内衬套D外,其余5种产品均拉伸强度> 1 MPa,断裂伸长率> 120.0%,100%定伸强度> 0.9 MPa。结论 因材料和生产工艺等原因6种样品的细胞毒性和力学性能有较大差异。     

Effect of benzoic acid surface modified alumina nanoparticles on the mechanical properties and crystallization behavior of isotactic polypropylene nanocomposites

The effect of benzoic acid (BA) surface modified alumina (Al₂O₃) nanoparticles (NPs) on the mechanical properties and crystallization behavior of isotactic polypropylene (iPP) nanocomposites was studied. Characterization of the modified Al₂O₃ NPs (BA-Al₂O₃) by FTIR and XRD analyses confirmed that benzoic acid molecules chemisorb on the surface of the NPs, forming benzene groups-rich microstructures. A considerable increase in the tensile strength, flexural modulus, and toughness was observed for the nanocomposites with only 0.2 wt% BA-Al₂O₃. Enhanced interfacial adhesion with the matrix was achieved, which enabled effective reinforcement of the nanocomposites. The higher crystallization temperature along with shorter crystallization halftime indicated the higher nucleation activity of BA-Al₂O₃. Furthermore, the interchain conformational ordering of iPP was significantly accelerated in the presence of the BA-Al₂O₃ NPs. The CH–π interaction between the polymer and BA-Al₂O₃ NPs was considered to facilitate the attachment of the iPP chains and stimulate conformational ordering, crystallization, as well as mechanical properties of nanocomposites.

The CH–π interactions between polypropylene and functionalized alumina (BA-Al₂O₃) nanoparticles improve the mechanical performance and conformational ordering of nanocomposites.     

热压膜材料的弯曲力学性能

背景:随着热压膜技术的发展,正畸临床上出现使用热压膜材料制作的改良矫治器.目的:观察不同厚度热压膜材料的弯曲力学性能差异.方法:在室温25 ℃环境下,选用厚度为1.0 mm,1.2 mm,1.5 mm,2.0 mm的热压膜膜片各10片,应用万能材料试验机测量并比较材料在未处理时(面积为40 mm×25 mm)和在不同长方形模具上热压膜成盒形时(体积均为50 mm×10 mm× 5 mm)的弯曲力学性能.结果与结论:在不同的处理方式下,2.0 mm热压膜膜片的弹性模量、屈服强度,最大值-应力均最高(P < 0.05),同时该材料未出现断裂点.证实,厚度和形状对热压膜材料的力学性能产生影响,2.0 mm热压膜的力学性能最高,适用于临床制作功能矫治器.     

A facile fabrication of porous fluoro-polymer with excellent mechanical properties based on high internal phase emulsion templating using PLA as co-stabilizer

The stability of fluoro-high internal phase emulsion (fluoro-HIPE) systems and fluoro-polyHIPEs’ mechanical strength require further improvement to meet the requirements of future applications. In this study, we used polylactic acid (PLA) as a co-stabilizer to improve the stability of the fluoro-polyHIPE. The effects of concentration and molecular weight of PLA on the pores of the fluoro-polyHIPEs were investigated. The addition of PLA produced a porous material with narrower void size distributions, higher specific surface areas and enhanced mechanical properties compared to the fluoro-polyHIPE material without the additive. The resulting fluoro-polyHIPE showed smaller pore sizes (void diameters ranged from 1–3 μm) and an improved hydrophobic nature (contact angle can reach to 148.6°). The crush strength and Young''s modulus values can reach 4.42 and 74.07 MPa, respectively, at a PLA addition of 25 wt% (oil phase composition), representing increases of 246% and 650% over fluoro-polyHIPE without PLA addition. The fluoro-poly-HIPE demonstrated excellent mechanical properties compared to many engineering foams, such as melamine, polystyrene, and even graphite foams. Improvements in the performance of porous fluoropolymer materials will be beneficial for many applications, such as chemical adsorption and separation, etc.

Effect of PLA on the stability of fluorinated-HIPE and size tuning of the resultant fluoro-polyHIPE with enhanced mechanical properties.     

Endotoxin and the mechanical properties of the canine peripheral circulation

To determine if alterations in venous vascular mechanics by endotoxin contribute to the hemodynamic disorder of septic shock, we studied eight dogs before and after the injection of 5 to 10 mg/kg of Escherichia coii endotoxin. We isolated the venous drainage of the peripheral (ie, superior plus inferior vena cava below the renal veins) and splanchnic vasculatures, and measured venous pressure (Pv) and flow (electromagnetic flow meter) in each region. Blood drained through vascular waterfalls that controlled the Pv of each region and then into a reservoir. A constant flow pump returned blood to the right atrium. By temporarily stopping all flows, we measured the elastic recoil pressures of each region. We changed regional volumes by changing Pv and integrating the transient changes of outflow. This allowed the calculation of compliance (Cv in mL/mm Hg/kg), venous resistance (Rv), venous time constant (τv in seconds), and fractional flow of each region. Endotoxin produced a large loss of reservoir volume but did not change the fractional flows. Peripheral Cv increased and Rv did not change, so that peripheral τv was 3.8 ± 1.0 before and 5.7 ± 2.7 (mean ± SD; P < .024) after endotoxin. The splanchnic compliance tended to decrease (0.776 ± 0.801 before and 0.487 ± 0.418 after; P = NS) and Rv did not change, so that splanchnic τv decreased from 14.6 ± 5.6 before to 10.8 ± 5.1 after endotoxin (P < .024). In the intact animal, without a reservoir, the decrease in stressed volume would decrease cardiac output and the decrease in the splanchnic τv would increase cardiac output.     

Inducing endoderm differentiation by modulating mechanical properties of soft substrates

Early embryonic stem cell (ESC) differentiation is marked by the formation of three germ layers from which all tissues types arise. Conventionally, ESCs are differentiated by altering their chemical microenvironment. Recently however, it was established that a mechanical microenvironment can also contribute towards cellular phenotype commitment. In this study, we report how the cellular mechanical microenvironment of soft substrates affects the differentiation and phenotypic commitment of ESCs. Mouse ESCs were cultured in a fibrin hydrogel matrix in 2D and 3D cultures. The gelation characteristics of the substrates were modulated by systematically altering the fibrinogen concentration and the fibrinogen‐thrombin crosslinking ratio. Analysis of the ESCs cultured on different substrate conditions clearly illustrated the strong influence that substrate physical characteristics assert on cellular behaviours. Specifically, it was found that ESCs had a higher proliferation rate in gels of lower stiffness. Early differentiation events were studied by analyzing the gene and protein expression levels of early germ layer markers. Our results revealed that lower substrate stiffness elicited stronger upregulation of endoderm related genes Sox17, Afp and Hnf4 compared to stiffer substrates. While both 2D and 3D cultures showed a similar response, the effects were much stronger in 3D culture. These results suggest that physical cues can be used to modulate ESC differentiation into clinically relevant tissues such as liver and pancreas. Copyright © 2012 John Wiley & Sons, Ltd.     

Inherent mechanical properties of bilayer germanene coupled by covalent bonding

Germanene, a two-dimensional buckled hexagonal structure of germanium atoms, has attractive mechanical, optical, thermal and electronic features. Recently it has been reported that covalent bonding between two monolayer germanene sheets leads to the integration of intrinsic magnetism and band gap opening that makes it attractive to future nanoelectronics. In order to use the captivating features of this structure, its mechanical characterization needs to be studied. In this study, molecular dynamics simulations have been performed using optimized Tersoff potential to analyze the effect of chirality, temperature and strain rate on the uniaxial tensile properties of this structure. This study suggests that bonded bilayer germanene shows higher mechanical strength compared to monolayer germanene. Uniaxial loading in the armchair direction shows higher fracture strength and strain compared to the zigzag direction which is contrary to the monolayer germanene. It also reports that with increasing temperature, both the fracture strength and strain of the structure decrease. It has been found that at a higher strain rate, the material exhibits higher fracture strength and strain. Mechanical properties and fracture mechanisms of defected structures have also been reported below the curie temperature. Moreover, the interlayer shear characteristics of the bilayer structure have been looked into. These results will provide significant insight to the investigation of this structure as a potential nano-electronics substitute.

Presence of interlayer bonds in bi-layer germanene results in a distinct fracture mechanism in tensile loading and direction dependent periodic behavior in shear loading.     

Alignment of the lower extremity mechanical axis by computer-aided design and application in total knee arthroplasty

Purpose

The success of total knee arthroplasty (TKA) depends on many factors. The position of a prosthesis is vitally important. The purpose of the present study was to evaluate the value of a computer-aided establishing lower extremity mechanical axis in TKA using digital technology.

Methods

A total of 36 cases of patients with TKA were randomly divided into the computer-aided design of navigation template group (NT) and conventional intramedullary positioning group (CIP). Three-dimensional (3D) CT scanning images of the hip, knee, and ankle were obtained in NT group. X-ray images and CT scans were transferred into the 3D reconstruction software. A 3D bone model of the hip, knee, ankle, as well as the modified loading, was reconstructed and saved in a stereolithographic format. In the 3D reconstruction model, the mechanical axis of the lower limb was determined, and the navigational templates produced an accurate model using a rapid prototyping technique. The THA in CIP group was performed according to a routine operation. CT scans were performed postoperatively to evaluate the accuracy of the two TKA methods.

Results

The averaged operative time of the NT group procedures was \(46.8\pm 9.1\) min shorter than those of the conventional procedures (\(57.5\pm 12.3\)  min). The coronal femoral angle, coronal tibial angle, posterior tibial slope were \(89.4^{\circ }\pm 1.5^{\circ }\), \(89.3^{\circ }\pm 1.4^{\circ }\), \(6.8^{\circ }\pm 1.6^{\circ }\) in NT group and \(87.3^{\circ }\pm 3.8^{\circ }\), \(88.1^{\circ }\pm 1.9^{\circ }\), \(10.9^{\circ }\pm 4.6^{\circ }\) in CIP group, respectively. Statistically significant group differences were found.

Conclusions

The navigation template produced through mechanical axis of lower extremity may provide a relative accurate and simple method for TKA.

     

人工椎体的组织相容性和力学性能

背景:近年来,随着组织工程学的发展,椎体替代材料趋于多样化,学者们不再满足于其能否恢复椎体高度与即刻稳定性,而是更为关注远期的融合,良好的组织相容性和力学性能。目的:分析国内人工椎体的组织相容性和力学性能。方法:以人工椎体、相容性、生物力学为检索词在中国期刊全文数据库中检索与人工椎体生物相容性和生物力学研究相关的文献进行分析。结果与结论:人工椎体组织相容性的动物实验显示,纳米羟基磷灰石/聚酰胺66复合人工椎体成分和结构与人体骨相似,具有良好的生物相容性,成骨活性;可发生生物降解,其降解作用与成骨能力匹配。人工椎体的生物力学研究显示出纳米羟基磷灰石/聚酰胺66复合人工椎体不仅具有良好的生物活性,而且具有良好的轴向压缩载荷和椎间支撑能力,力学性能优异。生物陶瓷人工椎体不仅具有良好的生物相容性,而且在治疗椎体肿瘤中有靶向定位作用;金属材料的人工椎体经过多年的改进,其生物相容性亦可满足临床要求。就各类型人工椎体优劣而言,仍需进一步大量研究和实践,就其临床应用而言,需根据临床需要进行选择。